1. Field of Invention
The present invention relates generally to preventing electrical potential non-uniformity on a photoreceptor surface.
2. Description of Related Art
In a typical electrostatographic printing process, printing is initiated by selectively charging and/or discharging a charge receptive imaging member, e.g., a photoreceptor, in accordance with an original input document or an imaging signal, thereby generating an electrostatic latent image on the imaging member. This latent image is subsequently developed into a visible image by a process in which a charged developing material is deposited onto the surface of the latent image bearing imaging member. The charged particles in the developing material adhere to image areas of the latent image to form a visible developed image corresponding to the latent image on the imaging member. The developed image may be subsequently transferred, either directly or indirectly, from the imaging member to a copy substrate, such as paper or the like, to produce a "hard copy" output document. In a final step, the imaging member is cleaned to remove any charge and/or residual developing material therefrom in preparation for a subsequent image forming cycle.
The developing material typically comprises carrier granules having toner particles adhering electrically thereto, wherein the toner particles are electrostatically attracted from the carrier granules to the latent image areas to create a powder toner image on the imaging member. Alternatively, the developing material may comprise a liquid developing material comprising a carrier liquid having pigmented marking particles, or "toner solids," and charge director materials dispersed and/or dissolved therein. When the liquid developing material is applied to the latent image bearing imaging member, the marking particles are attracted to the image areas of the latent image to form a developed liquid image. Regardless of the type of developing material employed, the toner or marking particles of the developing material are uniformly charged and are electrostatically attracted to the latent image.
The above-described electrostatographic printing process is well known and has been implemented in various forms in the marketplace to facilitate, for example, light lens copying of an original document, as well as printing of electronically generated or digitally stored images where the electrostatic latent image is formed via a modulated laser beam.
In an ionographic device, an ion producing device generates ions to be directed past a plurality of modulation electrodes to a charge receptive imaging member, e.g., charge receptor or photoreceptor. The ions are deposited on the charge receptor in an image-wise configuration to form an electrostatic latent image that may be developed directly on the charge receptor. A final substrate to be output, such as dielectric paper, may be used as the charge receptor, thus eliminating the need for a subsequent transfer of the developed image to a final output product. Alternatively, a drum, a belt, or the like, coated with insulating dielectric film may be used as the charge receptor. In this situation, the developed image is subsequently transferred from the charge receptor to a final substrate.
Analogous processes also exist in other electrostatic printing systems wherein a charge carrying medium is adapted to carry an electrostatic latent image. The typical electrostatographic printing process includes a development step whereby developing material is physically transported into contact with the imaging member so as to selectively adhere to the latent image areas thereon in an image-wise configuration. As discussed above, development of the latent image is usually accomplished by electrical attraction of the toner or marking particles to the image areas of the latent image. The development process is most effectively accomplished when the particles carry electrical charges opposite in polarity to the latent image charges, with the amount of toner or marking particles attracted to the latent image being proportional to the electrical field associated with the image areas. Some electrostatic imaging systems operate in a manner wherein the latent image includes charged image areas for attracting developer material, referred to as charged area development (CAD), or "write white" systems. Other printing processes operate in a manner such that discharged areas attract developing material, referred to as discharged area development (DAD), or "write black" systems.
As discussed above, in one electrostatic printing technique, latent electrostatic images are formed on a photoreceptor and are developed by a suitable toner material to render the images visible. The images are subsequently transferred to plain paper of various widths and thickness.